[FFmpeg-devel] MPEGTS stream auto-guessed before PMT is read

Stephen D'Angelo SDAngelo
Thu Nov 18 17:53:51 CET 2010


I have encountered transport streams where the AVStreams created are not
properly associated with the AVPrograms.  I'm no expert on the current
mpegts.c code, but I believe it is happening because of the following:

- The PMT for the stream's program is not read in mpegts_read_header
before auto_guess is turned on (line 1401)
- During av_find_stream_info, the pes stream is added to ts->pids in
handle_packet because auto_guess is true (line 1196)
- The PMT is read later and in pmt_cb the pes stream in found in
ts->pids, but pes->st has not been set yet, causing pmt_cb to return
(line 936)
- The AVStream for the pes stream is then added later in
mpegts_push_data (line 693), but it is not properly associated with its

The following patch fixes the problem by creating an AVStream for the
pes stream if it doesn't have one, and then the subsequent call to
ff_program_add_stream_index properly associates the AVStream with the

Index: libavformat/mpegts.c
--- libavformat/mpegts.c        (revision 25762)
+++ libavformat/mpegts.c        (working copy)
@@ -926,6 +926,8 @@
         if (ts->pids[pid] && ts->pids[pid]->type == MPEGTS_PES) {
             pes = ts->pids[pid]->u.pes_filter.opaque;
             st = pes->st;
+            if (!st)
+                st = pes->st = av_new_stream(pes->stream, pes->pid);
         } else {
             if (ts->pids[pid]) mpegts_close_filter(ts, ts->pids[pid]);
//wrongly added sdt filter probably
             pes = add_pes_stream(ts, pid, pcr_pid);

Would it instead make more sense to "add_pid_to_pmt" before checking
that there is no AVStream (line 936) and "continue" if there is no
AVStream (line 937) so that all of the pes streams are associated with
the program and then after calling av_new_stream in mpegts_push_data,
call ff_program_add_stream_index to associate the AVStream with its
AVProgram?  If it's done that way, the AVStream will not have the proper
language information that's added in pmt_cb.

 - Stephen

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